DEA ARD expanded processing extent

DEA produces surface reflectance products from Landsat and Sentinel-2 satellite observations which cover the continent and some near-shore islands of Australia. This data is used to produce derivative products such as DEA Coastlines, Water Observations, and Fractional Cover.

We are extending our baseline satellite data coverage to include Christmas Island, Cocos (Keeling) Islands, Coral Sea Islands, Heard and McDonald Islands, Norfolk Island, and islands in the Torres Strait. Additionally, we are processing imagery over shallow ocean areas to support bathymetry and oceanographic science.

The new data was requested by and will support Indigenous communities in the Torres Strait, in addition to Government agencies who seek to report on Ocean Ecosystem Accounts and manage the full extent of our Marine Parks.

The update will support the expansion of DEA’s Summary Product Grid, including a shift in the origin point to the south-west of its current position. The expanded Area of Interest will support several DEA product releases and version updates throughout 2024.

The standard ancillaries used to generate surface reflectance products over the mainland are of higher quality than those over extended offshore areas. For a detailed description of the difference, please see the sections below.

Additional locations

These maps represent all the additional locations that were added.

A map of Australia and surrounding areas annotated with rectangles to indicate the locations of additional Landsat scenes.

The locations of the additional Landsat scenes.

A map of Australia and surrounding areas annotated with rectangles to indicate the locations of additional Sentinel-2 scenes.

The locations of the additional Sentinel-2 scenes.

Full list of locations

This table contains the full list of locations, including the additional locations that were added.

Region

Scenes / Tiles

Heard Island and MacDonald Islands

134-097, 135-097, 136-097, 43FDA, 43FDB, 43FCB, 43FCA

Lord Howe Island

084-082, 085-082, 59JKJ, 58JGP, 59JKH, 58JGN

MacQuarie Island

080-098, 079-098, 079-099, 57FWU, 57FWV, 57FVV, 57FWA, 57FVA, 57FVU

Norfolk Island

079-080, 080-080, 57JWF, 57JVF, 57HVE, 57HWE

Christmas Island

122-067, 123-067, 48LWP, 48LXP

Cocos (Keeling) Island

128-068, 128-069, 47LKG, 47LKH, 46LHN, 46LHM

Talbot Islands, Dauan Island, Saibai Island and Boigu Island

099-066

Daru, Western Province Papua New Guinea and Northern Warrior Reefs

098-066, 54LZR

Elizabeth Reef

085-081, 57JVG, 57JWG

Middleton Reef

085-080, 57JVH, 57JWH

Frederick Reef, Queensland

088-075, 56KQB, 57KTS, 56KQA

Coral Sea – Scenes with Ocean depth less than 200m

089-072, 088-074, 088-076, 54LZL, 55KEA, 55KFV, 55KGA, 55KGV, 55KHA, 55KHT, 55KHU, 55LBF, 55LBJ, 55LBK, 55LCJ, 55LDC, 55LDE, 56KKC, 55KKD, 56KKF, 56KLC, 56KMV, 56KNU, 56KQA, 56KQB, 56KQF, 56KQG, 56KQV, 56KRB, 56KRF, 56KRG, 57KTA, 57KTB, 57KTS, 57KTS

Gulf of Carpentaria

101-069, 53LRC, 54LTH

Arafura Sea

102-067, 104-067, 106-067, 107-068, 107-069, 52LEM, 52LEN, 52LFP, 52LHP, 53LLJ, 53LPJ, 53LQH, 53LQJ

Timor Sea

51LVD, 51LWD, 51LWF, 51LXE, 51LXF, 51LYF, 51LZF, 52LBL, 52LCL, 52LDK

Indian Ocean

116-075, 49HGB, 49HGC, 49JFL, 49KGS, 49KHT, 50HKG, 50HKH, 50HKJ, 50HMF, 50HNF, 50JKL, 50KKC

Great Australian Bight

52HBI, 52HEK, 52HFK, 53HKD, 53HLC, 53HNA

Augusta, Western Australia

113-084

Tasman Sea

089-088, 089-091, 090-091, 55GFM

Bass Strait

54HXB

Quality and metadata

The quality of ancillary inputs used in ARD generation in offshore locations is limited in comparison to the higher quality ancillary inputs used on continental Australia. Quality information for ancillary inputs is found in the proc-info (processing information) YAML metadata file within the dataset. The tier list is USER, FALLBACK, and DEFINITIVE, with the latter being the highest level of quality. Unfortunately, this information is not available to users via the datacube, so we have added an additional metadata tag to delineate data delivered in this update: final_ancillaries = "nonstandard"

dc.find_datasets(product="ga_ls8c_ard_3", limit=10, final_ancillaries="nonstandard")

Geometric quality assessment issues

ARD is a Surface Reflectance product which is derived from USGS or ESA Level 1 products. The Level 1 product is geometrically corrected such that the product is ‘ortho-rectified’ which results in enabling acquisitions from different dates to be spatially overlaid for assessment through time. The ARD product provides a comprehensive quality assurance of geometric correction known as GQA, which is found in the dataset and processing information metadata.

This update features the addition of Landsat scenes and Sentinel 2 tiles over islands and reefs. Some of these islands, such as Christmas Island or islands south of Papua New Guinea, are at extreme high or low latitudes and are affected by persistent cloud. This presents challenges when correlating the reference image against source images to provide statistical geometric comparisons.

The following map represents the density of USGS Level 1 L1TP scenes over the extended area. These scenes are used as input for ARD generation and represent a higher geometric accuracy as ground control points and a digital elevation model is incorporated into ortho-processing. Locations with L1TP level 1 inputs are scenes which contain islands or land features which can be used as control. Locations entirely over shallow Ocean which have been added for bathymetric purposes have low geometric accuracy.

A map of Australia and surrounding areas annotated with rectangles representing density and coverage.

LS 5/7/8/9 L1TP Density and Coverage

BRDF quality issues

BRDF is a solar illumination correction which adjusts reflectance intensity in differing amounts in differing directions. The light that comes from the Sun, reflects off the Earth and is received by the sensor is adjusted based on viewing/solar angle geometries of MODIS data.

Sometimes over offshore locations we have found BRDF values to be unphysical. We have implemented a BRDF solution over the offshore locations, which masks out data from solar illumination correction where Fvol/Fiso or Fgeo/Fiso > 1. This ensures that we do not violate the theoretical definition of these parameters, meaning the values are realistic.

Water vapor

No ancillary source dataset difference between mainland and offshore locations.

Aerosol

A constant value of 0.06 Aerosol Optical Depth (AOD) is used as ancillary input as we do not have aerosol data for these extended locations. This constant value is based on the assumption that the average AOD data in Australian continental is around the 0.05, but islands are surrounded by the sea and impacted by salt water particles, so setting AOD as 0.06 is reasonable.

Ozone

The Ozone constant value for ancillary input is set to 0.275 ATM-CM. Typically in the extended offshore locations, Ozone is around 0.25 to 0.3. Ozone does not impact radiometric values in bands (wavelengths) by a significant amount.